With digitalization and high-performance of electronic products, as customer demands are changed, a flow of market demands has been changed to development of power supply devices having a thin type, a light weight, a high capacity due to high energy density.
In order to satisfy the customer demands, power supply devices such as a lithium ion secondary battery, a lithium ion polymer battery, and super capacitors (an electronic double layer capacitor and a pseudo capacitor) having a high energy density and a large capacity have been developed.
Recently, the demand for mobile electronic devices such as portable telephones, notebooks, and digital cameras is continuously increasing, and particularly, an interest in flexible mobile electronic devices applied with a rollable display, a flexible e-paper, a flexible liquid crystal display (flexible-LCD), a flexible organic light-emitting diode (flexible-OLED), and the like has been recently increased. Accordingly, it is required that a power supply device for the flexible mobile electronic device also have a flexible characteristic.
A flexible battery has been developed as one of the power supply devices capable of reflecting the characteristic.
The flexible battery may include a nickel-cadmium battery, a nickel-metal hydride battery, a nickel-hydrogen battery, a lithium-ion battery, and the like having a flexible property. Particularly, the lithium-ion battery has high availability due to high energy density per unit weight and quick charging compared to other batteries such as lead storage batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries.
The lithium-ion battery uses a liquid electrolyte and has been mainly used in a welded form by using a metal can as a container. However, a cylindrical lithium-ion battery using the metal can as the container has a disadvantage of limiting designs of electric products because the form is fixed and it is difficult to reduce a volume.
Particularly, as described above, the mobile electronic device is developed to be thinned, small-sized, and flexible, and thus there is a problem in that the lithium-ion battery using the metal can in the related art or a battery having a rectangular structure is not easily applied to the mobile electronic device.
Accordingly, in order to solve the structural problem, recently, a pouch type battery used by putting an electrolyte in a pouch including two electrodes and a separator and sealing the electrolyte has been developed.
The pouch type battery is made of a flexible material to be manufactured in various forms and has an advantage of implementing high energy density per mass.
That is, as illustrated in FIG. 1, a pouch type battery 1 is provided in a form in which an electrode assembly 20 is sealed at the inside of the exterior material 10, and the exterior material 10 has a laminated structure of an inner resin layer, a metal layer, and an outer resin layer. Among them, the metal layer is a required constitute element of the exterior material for moisture-proof and the like, and the metal layer may not pass through moisture and an electrolyte due to a dense density to prevent moisture from penetrating to the inside of the exterior material from the outside of the exterior material and simultaneously, prevent the electrolyte positioned in the exterior material from being leaked to the outside of the exterior material.
However, since the metal layer hardly ensures flexibility at a predetermined level or more due to insufficient elastic resilience, there is a problem in that cracks are caused in the flexible battery using the exterior material.
Further, in some cases, the pouch type battery 1 is implemented in a flexible form to be applied to products. However, since the pouch type battery 1 in the related art is implemented in a simply flexible form, when repeated bending occurs in a using process, the exterior material and the electrode assembly are repetitively contracted and relaxed to be broken or the performance is significantly reduced compared to an initial design value, and thus there is a limit to exhibit a function as the battery.